Octylated/butylated diphenylamine is a known antioxidant for a variety of organic materials. This is taught for example in U.S. Pat. No. 4,824,601.
Phenothiazine is a known antioxidant for organic materials.
Octadecyl (3,5-di-tert-butyl-4-hydroxyphenyl)-propionate is a well known phenolic antioxidant for organic materials. This is disclosed for example in U.S. Pat. No. 4,228,297.
Liquid mixtures of antioxidant packages are desirable for plastics manufacturing purposes. Two part mixtures of octylated/butylated diphenylamine and phenothiazine are not stable liquids under ambient conditions. Surprisingly, it has been found that addition of low levels of the further antioxidant octadecyl (3,5-di-tert-butyl-4-hydroxyphenyl)-propionate allow the mixture to be liquid at certain temperatures.